In a usual production utilizing stop-motion animation, the producers determine the position of the animated three dimensional object in each film frame usually by intuition. As it is nearly always impossible when producing stop motion animation to know, for example, precisely how much a figure's arm has moved in the last frame photographed and needs to move in the next, the producer must rely on his sixth sense to make the adjustment. This production method has a great disadvantage as the resulting movement of the three-dimensional figure or object in the final film produced looks slightly snappy or jerky, and lacks smoothness and realism. This jerkiness and lack of realism is present in virtually all films produced using stop-motion animation, even in films produced by those highly skilled in the art, and remains today the outstanding problem associated with stop-motion animation. The present invention is concerned with eliminating this problem.
Attempts have been made in the past to develop several techniques and inventions in order to eliminate such jerky movement and to impart instead greater realism to the production of stopmotion animation. All such prior techniques, however, have inherent disadvantages, which will be discussed.
One prior approach, disclosed in U.S. Pat. No. 2,241,929, utilizes an arrangement of steps including first making a series of drawings representing the object to be animated in various sequential positions, producing a film strip from the resultant drawing series, sequentially projecting the film strip frames onto a screen, sequentially posing the object in conformity with the projected screen image that is behind the object, and finally, sequentially photographing the object in its posed positions for the production of a finished film.
This prior method allowed the producers of the stopmotion animated film a degree of planning with regard to the object to be animated. However, the technique had a disadvantage in that at best one could only match the outline of the object to the projected image on the screen (in this technique's most precise form, one matches the object's shadow cast on the screen to the projected film image on the screen); it is thus impossible to determine the required location of those portions of the object within the object's outline. For example, in the case of a humanlike doll seen walking in profile in a position in which its arm is within its body's outline, and does not extend from the body, it would be impossible to determine the exact location of the arm in this posed position. Therefore, this technique lacks precision. Another technique in this patent calls for alignment of interior features by projecting the animation frame directly onto the puppet. Such a technique is imprecise because of the difficulty in determining the precise point at which a line begins and ends. In addition, all lines of a frame may not be projected on the unposed puppet, for example the succeeding frame may contain an extended arm with portions oriented considerable higher than the present position of the posed puppets arm. Furthermore, some of the projected lines may be out of focus on the 3-dimensional puppet.
Another technique, disclosed in U.S. Pat. No. 2,358,530, utilized an alignment grid composed of a series of squares. This grid was in close proximity to the puppet or object to be animated in the usually (stop-motion fashion. After posing the puppet in one position, one noted the positions of the arms, legs, etc., onto the grid, and then utilized these grid notations for reference while posing the doll in the next position, repeating this process throughout the film's production. The disadvantage of this prior technique is, firstly, that it allows no extensive preplanning of the puppet's posed positions such as in the prior technique previously discussed, because one is noting positions only after they have been set. Secondly, the technique allows one to note only the positions of those portions of the body which are on the outline of the body, and not within. This approach results in the same problem which existed in the technique previously discussed: lack of precision.
Another prior art technique, disclosed in U.S. Pat. No. 2,599,624, made use of a similar type of alignment grid. Specifically, in this arrangement, two alignment grids were utilized to coordinate the positions of a puppet with a previously filmed sequence of a live actor (which is projected in close proximity to the puppet). The disadvantage of this system is that the movements of the puppets must be based on the movements of what the invention terms "live talent" --that is, the movement of humans or animals. This is limiting to the producer of stop-motion of imaginary creatures, such as dinosaurs or 3-headed dragons, of which no previously filmed "live talent" exists. This is a severe disadvantage as stop-motion animation is very often utilized precisely because it is the only method known in which imaginary creatures can come to life. Also, in this method there is no precise visual superimposition of the object and live actor's respective positions, as a side-by-side comparison requires a subjective, thus approximate, positioning of the puppet.
Another prior art technique, disclosed in U.S. Pat. No. 3,970,379, attempted to impart greater realism to stop-motion animation by sequentially projecting (from above the stage) a film of predetermined indices onto the stage upon which the three dimensional puppets or objects rest, sequentially posing the puppets or objects on the stage in conformity with the projected indices, and sequentially photographing the puppets or objects in their posed positions for the production of a finished film. The disadvantage of this scheme is that while it made the smooth movement of the puppets or objects about the stage possible, it did not provide indices for the movement of animatable portions of the puppets or objects' bodies, such as their arms or legs (it only provided indices for the puppets' or objects' stage movement). As a result, a puppet may move about the stage fairly smoothly but still move its arms, legs, head, etc., in the slightly jerky and unrealistic fashion that is typical of stop-motion animation.
Yet another prior art technique, disclosed in U.S. Pat. No. 3,081,667, attempted to impart greater realism to puppet or doll-films in an especially ingenious way. Through the utilization of a scheme involving a camera, a projector, and a semi-transparent mirror, one was able to superimpose the position of the puppet that one was animating in the usual frame-by-frame fashion with the image of a living being (such as an actor) that is projected frame-by-frame from a previously photographed motion-picture film. This prior approach no doubt made possible the production of more realistic puppet and doll-films, but the approach has the same severe disadvantage as previously noted with U.S. Pat. No. 2,599,624. As the movement of the puppet or doll is based upon the movement of what the inventor himself terms a "living creature" (the creature being previously photographed onto motion picture film), the invention does not make possible the realistic movement of puppets or dolls which are imaginary creatures, such as dinosaurs or dragons, as no living creature exists upon which one can base the movements. As was the case in the previously discussed technique, this approach severely limits the producer of the stop-motion animated film. Stop-motion animation is often utilized precisely for this purpose, it being the only known method of bringing such imaginary three-dimensional creatures to life. Furthermore, the comparison is done only from one angle (one dimension) and does not allow for camera motions which were not pre-determined during the filming of the "living being" reference, thus depriving the director of a precious element of last minute creativity.
Computer animation techniques are described in U.S. Pat. No. 4,600,919, for example. In that patent key frames were generated and stored, each key frame having a common figure of one or more joints. Each joint is defined by operator-controllable parameters which determine the three-dimensional position, rotational orientation and scale factors of a local coordinate system. A computer generates a plurality of in-between frames from the key frames by interpolating in three dimensions the position, rotational orientation and scale factors of the corresponding joints of the key frames. In one aspect, the operator can control the interpolation process during display of the in-between frame sequence in order to change or modify the motion of a figure limb. This reference relates to computer generated animation, rather than stop frame animation formed by sequentially positioning an object or model.
The disadvantages of the prior art relating to stop frame animation are overcome by the present invention.